(1) Field of the Invention
The invention relates to a method of barrier layer formation in the fabrication of integrated circuits, and more particularly, to a method of forming an optimized tantalum carbide nitride barrier layer to prevent copper diffusion in the manufacture of integrated circuits.
(2) Description of the Prior Art
In a common application for integrated circuit fabrication, a contact/via opening is etched through an insulating layer to an underlying conductive area to which electrical contact is to be made. A barrier layer, typically titanium nitride, is formed within the contact/via opening. A conducting layer material, typically tungsten, is deposited within the contact/via opening. As device sizes continue to shrink, these typical materials are no longer adequate. Because of its lower bulk resistivity, Copper (Cu) metallization is the future technology for feature sizes of 0.18 microns and below. Cu metallization requires a robust diffusion barrier to prevent the copper from diffusing through the active junctions.
U.S. Pat. No. 5,744,394 to Iguchi et al discloses a barrier layer that may comprise TaN, TaC, or TaNC. U.S. Pat. No. 5,973,400 to Murakami et al discloses a barrier layer comprising TaC or TaNC. While these two patents disclose a TaNC barrier layer, they do not specify the optimal nitrogen concentration within the film which will maximize simultaneously the barrier properties and low electrical resistivity. U.S. Pat. No. 4,985,750 to Hoshino shows a Ta or TaN barrier layer. U.S. Pat. Nos. 6,100,587 to Merchant et al and 6,028,359 to Merchant et al teach barrier layers of TaC, TaN, or TaB.
A principal object of the present invention is to provide an effective and very manufacturable method of forming a robust barrier layer in a copper metallization process in the fabrication of integrated circuit devices.
Another object of the invention is to provide a method for forming a tantalum carbide nitride barrier layer that will prevent copper diffusion in the fabrication of integrated circuit devices.
A further object of the invention is to provide a method for forming a tantalum carbide nitride diffusion barrier layer having optimized nitrogen concentration for improved thermal stability.
In accordance with the objects of this invention a new method of forming a tantalum carbide nitride diffusion barrier layer having optimized nitrogen concentration for improved thermal stability is achieved. A contact region is provided in a substrate. A via is opened through an insulating layer to the contact region. A tantalum carbide nitride barrier layer is deposited within the via wherein the tantalum carbide nitride layer has an optimized nitrogen content of between about 17% and 24% atomic percentage. A layer of copper is deposited overlying the tantalum carbide nitride barrier layer to complete copper metallization in the fabrication of an integrated circuit device.